483979-48-2Relevant articles and documents
Proton electroreduction catalyzed by cobaloximes: Functional models for hydrogenases
Razavet, Mathieu,Artero, Vincent,Fontecave, Marc
, p. 4786 - 4795 (2005)
Cobaloximes have been examined as electrocatalysts for proton reduction in nonaqueous solvent in the presence of triethylammonium chloride. [Co III(dmgH)2pyCl], working at moderate potentials (-0.90 V/(Ag/AgCl/3 mol·L-1 NaCl) and in neutral conditions, is a promising catalyst as compared to other first-row transition metal complexes which generally function at more negative potentials and/or at lower pH. More than 100 turnovers can be achieved during controlled-potential electrolysis without detectable degradation of the catalyst. Cyclic voltammograms simulation is consistent with a heterolytic catalytic mechanism and allowed us to extract related kinetic parameters. Introduction of an electron-donating (electron-withdrawing) substituent in the axial pyridine ligand significantly increases (decreases) the rate constant of the catalytic cycle determining step. This effect linearly correlates with the Hammet coefficients of the introduced substituents. The influence of the equatorial glyoxime ligand was also investigated and the capability of the stabilized BF2-bridged species [Co(dmgBF2)2(OH2)2] for electrocatalyzed hydrogen evolution confirmed.
Photocatalytic H2 production on hybrid catalyst system composed of inorganic semiconductor and cobaloximes catalysts
Wen, Fuyu,Yang, Jinhui,Zong, Xu,Ma, Baojun,Wang, Donge,Li, Can
, p. 318 - 324 (2011)
An artificial photocatalytic system mimicking photosystem I (PSI) has been assembled using semiconductor (CdS) as photosensitizer, cobaloximes (Co III complexes) as H2 evolution catalysts, and triethanolamine (TEOA) as sacrificial electron donor. This artificial photocatalytic system shows high hydrogen evolution activity (turnover number up to 171 based on CoIII(dmgH)2pyCl 1) under visible light irradiation. The apparent quantum efficiency (QE) for 1/CdS hybrid photocatalytic system in acetonitrile solution at 420 nm is calculated to be 9.1%. The interfacial electron transfer from photoexcited CdS to Co III complexes is very efficient through the weak adsorption of CoIII complexes on CdS. The adsorption of 1 on CdS in acetonitrile fits Langmuir equation, the maximum monolayer adsorption capacity is 3 × 10-3 mmol g-1, which means most of 1 are in the solution. The rate of hydrogen production exhibits a quadratic dependence on the total concentration of 1. Therefore, a bimetallic catalysis pathway is proposed. The efficient electron transfer, the broad electronic absorption character of CdS photosensitizer as well as the H2 evolution ability of Co III complexes, account for the high photocatalytic activity of this hybrid photocatalytic system.
Visible light-driven hydrogen production from aqueous protons catalyzed by molecular cobaloxime catalysts
Du, Pingwu,Schneider, Jacob,Luo, Genggeng,Brennessel, William W.,Eisenberg, Richard
, p. 4952 - 4962 (2009)
A series of cobaloxime complexes-([Co(dmgH)2pyCI] (1), [Co(dmgH)2(4-COOMe-py)CI] (2), [Co(dmgH)2(4-Me 2N-py)CI] (3), [Co(dmgH)(dmgH2)CI2] (4), [Co(dmgH)2(py)2](PF
A de novo Synthesis of Oxindoles from Cyclohexanone-Derived γ-Keto-Ester Acceptors Using a Desaturative Amination-Cyclization Approach
Caldora, Henry P.,Govaerts, Sebastian,Dighe, Shashikant U.,Turner, Oliver J.,Leonori, Daniele
supporting information, p. 4272 - 4278 (2021/08/13)
Here we report a desaturative approach for oxindole synthesis. This method uses simple ethyl 2-(2-oxocyclohexyl)acetates and primary amine building blocks as coupling partners. A dual photoredox cobalt manifold is used to generate a secondary aniline that, upon heating, cyclizes with the pendent ester functionality. The process operates under mild conditions and was applied to the modification of several amino acids, the blockbuster drug mexiletine, as well as the formation of dihydroquinolinones.
Photoredox/Cobalt Dual-Catalyzed Decarboxylative Elimination of Carboxylic Acids: Development and Mechanistic Insight
Cartwright, Kaitie C.,Joseph, Ebbin,Comadoll, Chelsea G.,Tunge, Jon A.
, p. 12454 - 12471 (2020/09/09)
Recently, dual-catalytic strategies towards the decarboxylative elimination of carboxylic acids have gained attention. Our lab previously reported a photoredox/cobaloxime dual catalytic method that allows the synthesis of enamides and enecarbamates directly from N-acyl amino acids and avoids the use of any stoichiometric reagents. Further development, detailed herein, has improved upon this transformation's utility and further experimentation has provided new insights into the reaction mechanism. These new developments and insights are anticipated to aid in the expansion of photoredox/cobalt dual-catalytic systems.
Photo-induced Decarboxylative Heck-Type Coupling of Unactivated Aliphatic Acids and Terminal Alkenes in the Absence of Sacrificial Hydrogen Acceptors
Cao, Hui,Jiang, Heming,Feng, Hongyu,Kwan, Jeric Mun Chung,Liu, Xiaogang,Wu, Jie
supporting information, p. 16360 - 16367 (2018/11/27)
1,2-Disubstituted alkenes such as vinyl arenes, vinyl silanes, and vinyl boronates are among the most versatile building blocks that can be found in every sector of chemical science. We herein report a noble-metal-free method of accessing such olefins through a photo-induced decarboxylative Heck-type coupling using alkyl carboxylic acids, one of the most ubiquitous building blocks, as the feedstocks. This transformation was achieved in the absence of external oxidants through the synergistic combination of an organo photo-redox catalyst and a cobaloxime catalyst, with H2 and CO2 as the only byproducts. Both control experiments and DFT calculations supported a radical-based mechanism, which eventually led to the development of a selective three-component coupling of aliphatic carboxylic acids, acrylates, and vinyl arenes. More than 90 olefins across a wide range of functionalities were effectively synthesized with this simple protocol.
External Oxidant-Free Oxidative Cross-Coupling: A Photoredox Cobalt-Catalyzed Aromatic C-H Thiolation for Constructing C-S Bonds
Zhang, Guoting,Liu, Chao,Yi, Hong,Meng, Qingyuan,Bian, Changliang,Chen, Hong,Jian, Jing-Xin,Wu, Li-Zhu,Lei, Aiwen
supporting information, p. 9273 - 9280 (2015/08/11)
An external oxidant-free oxidative coupling for aromatic C-H thiolation by visible-light photoredox cobalt-catalysis has been developed. Various substrates could afford benzothiazoles in good to excellent yields, and only H2 is generated as a side product. When catalytic TBAOH was used as the base, not only 2-aryl but also 2-alkylbenzothiazoles could be obtained through this novel dehydrogenative coupling reaction. This method could be scaled up and applied to the synthesis of biologically active molecules bearing benzothiazole structural scaffolds (potent antitumor agents). Furthermore, the unexpected oxidation byproduct amides, which are often generated in oxidative cyclization of thiobenzanilides, can be completely avoided. Mechanistic studies showed that the H2 originates from the substrates. The kinetic studies indicate that the interaction between the cobalt catalyst and proton might be involved in the rate-limiting process. (Chemical Equation Presented).
Models for B12-conjugated radiopharmaceuticals. Cobaloxime binding to new fac-[Re(CO)3(Me2bipyridine)(amidine)]BF4 complexes having an exposed pyridyl nitrogen
Lewis, Nerissa A.,Marzilli, Patricia A.,Fronczek, Frank R.,Marzilli, Luigi G.
supporting information, p. 11096 - 11107 (2015/02/19)
New mononuclear amidine complexes, fac-[Re(CO)3(Me2bipy)(HNC(CH3)-(pyppz))]BF4 [(4,4′-Me2bipy (1), 5,5′-Me2bipy (2), and 6,6′-Me2bipy (3)] (bipy = 2,2′-bipyridine), were synthesized by treating the parent fac-[ReI(CO)3(Me2bipy)(CH3CN)]BF4complex with the C2-symmetrical amine 1-(4-pyridyl)piperazine (pyppzH). The axial amidine ligand has an exposed, highly basic pyridyl nitrogen. The reaction of complexes 1-3 with a B12model, (py)Co(DH)2Cl (DH = monoanion of dimethylglyoxime), in CH2Cl2 yielded the respective dinuclear complexes, namely, fac-[Re(CO)3(Me2bipy)(μ-(HNC(CH3)(pyppz)))Co-(DH)2Cl]BF4 [(4,4′-Me2bipy (4), 5,5′-Me2bipy (5), and 6,6′-Me2bipy (6)]. 1H NMR spectroscopic analysis of all compounds and single-crystal X-ray crystallographic data for 2, 3, 5, and 6 established that the amidine had only the E configuration in both the solid and solution states and that the pyridyl group is bound to Co in 4-6. Comparison of the NMR spectra of 1-3 with spectra of 4-6 reveals an unusually large wrong-way upfield shift for the pyridyl H2/6 signal for 4-6. The wrong-way H2/6 shift of (4-Xpy)Co(DH)2Cl (4-Xpy = 4-substituted pyridine) complexes increased with increasing basicity of the 4-Xpy derivative, a finding attributed to the influence of the magnetic anisotropy of the cobalt center on the shifts of the 1H NMR signals of the pyridyl protons closest to Co. Our method of employing a coordinate bond for conjugating the fac-[ReI(CO)3] core to a vitamin B12 model could be extended to natural B12derivatives. Because B12 compounds are known to accumulate in cancer cells, such an approach is a very attractive method for the development of 99mTc and 186/188Re radiopharmaceuticals for targeted tumor imaging and therapy. (Chemical Equation Presented).
